The invention relates to methods and apparatus for theft deterrence. More particularly, the invention relates to article surveillance techniques and systems.
Article surveillance systems are known in the art. Theft from retail establishments is a major problem, and article surveillance systems attempt to address this problem. To control theft, tags are secured to merchandise, and these tags must be removed or deactivated prior to removal of merchandise from a store or controlled area. If a tag is not removed or deactivated before merchandise is removed, detection equipment or a sensor near an exit will detect the tag and trigger an alarm and/or cause doors past the sensor to become locked.
Various designs of article surveillance systems are known in the art. The tag may include, for example, an electrical circuit which is designed to be resonant at a particular frequency, and the detection equipment may include, for example, two antennas. One of the antennas radiates electrical signals in a band of frequencies that includes the resonant frequency of the tag. The other antenna is tuned to receive signals. Antenna pairs (also known as pedestals) can be positioned to bracket a path or exit such that the only way for a person to exit out of a store or leave a secured area requires passing in between the two antennas. One such antenna pair is described in greater detail in U.S. Pat. No. 6,061,552 to Cerasini et al., which is incorporated herein by reference.
Some tags are permanently deactivatable by applying excessive energy to a resonant circuitry. The excess energy causes a resonant circuit to become deactivated by, for example, causing normally non-conductive material to become conductive. See, for example, U.S. Pat. No. 5,006,856 to Benge et al., which is incorporated herein by reference. Various designs for devices for deactivating tags are described in the following U.S. patents which are incorporated herein by reference: U.S. Pat. No. 5,949,318 to Copeland et al.; U.S. Pat. No. 5,990,794 to Alicot et al.; U.S. Pat. No. 6,011,474 to Coffey et al.; U.S. Pat. No. 6,061,552 to Cerasini et al.; and U.S. Pat. No. 6,281,796 to Canipe et al.
Some tags are capable of being reactivated after being deactivated (e.g., they are reusable). These designs typically involve use of magnetic principles. Attention is directed to the following U.S. patents which relate generally to anti-theft tags, deactivation devices, and pedestals and which are incorporated herein by reference: U.S. Pat. No. 3,895,368 to Gordon et al.; U.S. Pat. No. 3,995,900 to Humble et al.; U.S. Pat. No. 4,063,229 to Welsh et al.; U.S. Pat. No. 4,510,489 to Anderson et al.; U.S. Pat. No. 4,660,025 to Humphrey; U.S. Pat. No. 4,686,516 to Humphrey; U.S. Pat. No. 5,313,192 to Ho et al.; U.S. Pat. No. 5,495,230 to Lian; U.S. Pat. No. 5,729,200 to Copeland et al.; U.S. Pat. No. 5,942,978 to Shafer; U.S. Pat. No. 5,955,951 to Wischerop et al.; U.S. Pat. No. 5,963,173 to Lian et al.; U.S. Pat. No. 6,307,474 to Lian et al.; U.S. Pat. No. 6,320,507 to Strzelec et al.; U.S. Pat. No. 6,339,378 to Seidel; U.S. Pat. No. 6,351,216 to Frederick et al.; and U.S. Pat. No. 6,352,606 to DiMarco et al.
Attention is also directed to an article titled xe2x80x9cAntishoplifting Labels,xe2x80x9d by Joseph Ryan, Jr., appearing in the Working Knowledge column of Scientific American magazine, May 1997 issue, page 120. This article describes an antishoplifting system that includes a pedestal that brackets a store entrance or checkout aisle and contains a unit that transmits low radio frequency pulses; e.g., 58 kHz. The system further includes a product label including a resonator configured to vibrate at a frequency identical to the transmitted frequency; e.g., 58 kHz, when passed through the pedestal. The product label includes a magnetized strip adjacent to the resonator to ensure that the oscillations of the resonator remain precisely at the transmitted frequency; e.g., 58 kHz. A deactivation device can turn off a label when merchandise is paid for by demagnetizing the strip or altering its magnetic properties such that the resonator either will not vibrate or will do so at a frequency different from the transmitted frequency. A receiver inside one of the pedestal arms turns on between each transmitted pulse (e.g., during an 11 millisecond interval between each transmitted pulse) so that it can pick up the identical signal emitted by the label. If it receives a signal at least four times, an alarm is triggered.
Surveillance tags bearing coded indicia such as bar codes are known in the art. See, for example, U.S. Pat. No. 5,979,758 to Swartz et al., which is incorporated herein by reference.
The invention provides a reusable security tag, which is reversibly operable in a first magnetic condition, to trigger a detector when the tag is within communication range of the detector, and a second magnetic condition, in which the detector is not triggered when the tag is within communication range of the detector. The tag includes an optical indicator which has a first optical characteristic when the tag is in the first magnetic condition, and a second optical characteristic when the tag is in the second magnetic condition.
One aspect of the invention includes a surveillance system comprising a tag selectively switchable between an active state and an inactive state, the tag including an optical indicator configured to provide an optical indication of whether the tag is in the active state or the inactive state; a first antenna; a second antenna; a transmitter coupled to the first antenna and configured to transmit energy having a predetermined characteristic in an area between the first and second antennas, the tag providing a predetermined detectable output in response to the energy from the transmitter if the tag is in the active state; and a receiver coupled to the second antenna and configured to provide an alarm signal in response to detecting the detectable output of the tag in the area.